Response is very difficult... [&:] Lots of parameters here. I have some old flying machines (20 years old, glider) that are still flying with original servos of thoses years. Two weeks ago I've changed two servo on another that were erractic one's after ten years of servicing and at least the two last years without flights (propelled working plane, tug).

I don't know I we can even qualify parameters to make a choice of change or not.

The very same servo can live 20 years on a 20kg soft glider but being killed in one season of 3D flight with a 5kg propelled plane or 90 class 3D copter...

What about with our jets ? No vibration or few for sure, but efforts ?

Interresting question.